Add margins with basic box layouter 📖

src/doc.rs

@@ -1,7 +1,7 @@
 //! Representation of typesetted documents.
 
 use crate::font::Font;
-use crate::layout::Size;
+use crate::layout::{Size, Position};
 
 
 /// A complete typesetted document, which can be exported.
@@ -28,7 +28,7 @@ pub struct Page {
 #[derive(Debug, Clone)]
 pub enum TextAction {
     /// Move from the _start_ of the current line by an (x, y) offset.
-    MoveNewline(Size, Size),
+    MoveNewline(Position),
     /// Write text starting at the current position.
     WriteText(String),
     /// Set the font by index and font size.

src/layout/boxed.rs

@@ -0,0 +1,37 @@
+//! Layouting of layout boxes.
+
+use crate::doc::TextAction;
+use super::{Layouter, Layout, LayoutContext, LayoutResult, Position};
+
+
+/// Layouts sublayouts within the constraints of a layouting context.
+#[derive(Debug)]
+pub struct BoxLayouter<'a, 'p> {
+    ctx: &'a LayoutContext<'a, 'p>,
+    actions: Vec<TextAction>,
+}
+
+impl<'a, 'p> BoxLayouter<'a, 'p> {
+    /// Create a new box layouter.
+    pub fn new(ctx: &'a LayoutContext<'a, 'p>) -> BoxLayouter<'a, 'p> {
+        BoxLayouter {
+            ctx,
+            actions: vec![],
+        }
+    }
+
+    /// Add a sublayout.
+    pub fn add_layout_absolute(&mut self, position: Position, layout: Layout) {
+        self.actions.push(TextAction::MoveNewline(position));
+        self.actions.extend(layout.actions);
+    }
+}
+
+impl Layouter for BoxLayouter<'_, '_> {
+    fn finish(self) -> LayoutResult<Layout> {
+        Ok(Layout {
+            extent: self.ctx.max_extent.clone(),
+            actions: self.actions
+        })
+    }
+}

src/layout/mod.rs

@@ -6,9 +6,11 @@ use crate::syntax::{SyntaxTree, Node};
 
 mod size;
 mod text;
+mod boxed;
 
-pub use size::Size;
+pub use size::{Size, Position, Extent};
 pub use text::TextLayouter;
+pub use boxed::BoxLayouter;
 
 
 /// Layout a syntax tree in a given context.
@@ -44,7 +46,7 @@ pub fn layout(tree: &SyntaxTree, ctx: &LayoutContext) -> LayoutResult<Layout> {
 #[derive(Debug, Clone)]
 pub struct Layout {
     /// The extent of this layout into all directions.
-    extent: LayoutDimensions,
+    extent: Extent,
     /// Actions composing this layout.
     actions: Vec<TextAction>,
 }
@@ -75,20 +77,11 @@ pub struct LayoutContext<'a, 'p> {
     /// Loads fonts matching queries.
     pub loader: &'a FontLoader<'p>,
     /// The spacial constraints to layout in.
-    pub max_extent: LayoutDimensions,
+    pub max_extent: Extent,
     /// Base style to set text with.
     pub text_style: TextStyle,
 }
 
-/// A space to layout in.
-#[derive(Debug, Clone)]
-pub struct LayoutDimensions {
-    /// Horizontal extent.
-    pub width: Size,
-    /// Vertical extent.
-    pub height: Size,
-}
-
 /// Default styles for text.
 #[derive(Debug, Clone)]
 pub struct TextStyle {

src/layout/size.rs

@@ -6,6 +6,24 @@ use std::iter::Sum;
 use std::ops::*;
 
 
+/// A position in 2-dimensional space.
+#[derive(Debug, Copy, Clone, PartialEq, Default)]
+pub struct Position {
+    /// The horizontal coordinate.
+    pub x: Size,
+    /// The vertical coordinate.
+    pub y: Size,
+}
+
+/// Size of a box in 2-dimensional space.
+#[derive(Debug, Copy, Clone, PartialEq, Default)]
+pub struct Extent {
+    /// The horizontal extent.
+    pub width: Size,
+    /// The vertical extent.
+    pub height: Size,
+}
+
 /// A general spacing type.
 #[derive(Copy, Clone, PartialEq, Default)]
 pub struct Size {

src/layout/text.rs

@@ -7,7 +7,7 @@ use smallvec::SmallVec;
 
 use crate::doc::TextAction;
 use crate::font::{Font, FontQuery};
-use super::{Layouter, Layout, LayoutError, LayoutContext, Size, LayoutResult};
+use super::{Layouter, Layout, LayoutError, LayoutContext, LayoutResult, Size, Position};
 
 
 /// Layouts text within the constraints of a layouting context.
@@ -208,10 +208,11 @@ impl<'a, 'p> TextFinisher<'a, 'p> {
 
     /// Move to the top-left corner of the layout space.
     fn move_start(&mut self) {
-        self.actions.push(TextAction::MoveNewline(
-            Size::zero(), self.layouter.ctx.max_extent.height
+        self.actions.push(TextAction::MoveNewline(Position {
+            x: Size::zero(),
+            y: self.layouter.ctx.max_extent.height
                 - Size::from_points(self.layouter.ctx.text_style.font_size)
-        ));
+        }));
     }
 
     /// Move to the next line. A factor of 1.0 uses the default line spacing.
@@ -221,7 +222,11 @@ impl<'a, 'p> TextFinisher<'a, 'p> {
                 * self.layouter.ctx.text_style.line_spacing
                 * factor;
 
-            self.actions.push(TextAction::MoveNewline(Size::zero(), -vertical));
+            self.actions.push(TextAction::MoveNewline(Position {
+                x: Size::zero(),
+                y: -vertical
+            }));
+
             self.current_width = Size::zero();
         }
     }

src/lib.rs

@@ -48,7 +48,7 @@ use std::fmt::{self, Debug, Formatter};
 use crate::doc::Document;
 use crate::font::{Font, FontLoader, FontProvider};
 use crate::func::Scope;
-use crate::layout::{layout, Layout, LayoutContext, LayoutDimensions};
+use crate::layout::{layout, Layout, Layouter, LayoutContext, BoxLayouter, Extent, Position};
 use crate::layout::{PageStyle, TextStyle, LayoutResult, LayoutError};
 use crate::parsing::{parse, ParseContext, ParseResult, ParseError};
 use crate::syntax::SyntaxTree;
@@ -115,21 +115,34 @@ impl<'p> Typesetter<'p> {
     }
 
     /// Layout a syntax tree and return the layout and the referenced font list.
-    #[inline]
     pub fn layout(&self, tree: &SyntaxTree) -> LayoutResult<(Layout, Vec<Font>)> {
         let loader = FontLoader::new(&self.font_providers);
 
+        // Prepare the layouting context.
         let page = &self.page_style;
-        let ctx = LayoutContext {
+        let mut ctx = LayoutContext {
             loader: &loader,
             text_style: self.text_style.clone(),
-            max_extent: LayoutDimensions {
+            max_extent: Extent {
                 width: page.width - page.margin_left - page.margin_right,
                 height: page.height - page.margin_top - page.margin_bottom,
             },
         };
 
-        let layout = layout(&tree, &ctx)?;
+        // Layout the content of the page (without margins).
+        let content = layout(&tree, &ctx)?;
+
+        // Adjust the context for adding the margins.
+        ctx.max_extent = Extent {
+            width: page.width,
+            height: page.height,
+        };
+
+        // Add the margins.
+        let mut box_layouter = BoxLayouter::new(&ctx);
+        let start = Position { x: page.margin_left, y: page.margin_top };
+        box_layouter.add_layout_absolute(start, content);
+        let layout = box_layouter.finish()?;
 
         Ok((layout, loader.into_fonts()))
     }